Definition of swing
When we talk about poker swings, we are talking about upswings and downswings in terms of buy-ins. There are upswings and downswings. When you win a lot of buy-ins, it's called an upswing. When the opposite is true, it is called a downswing. A downswing is caused by variance in poker (upswings too). When a negative variance hits you and you lose multiple buy-ins, you are said to be downswinging. Downswing can also be caused by tilt or fatigue. It is not always clear what exactly causes downswing.
Bad luck or bad play?
Sometimes losses are caused by bad luck, but sometimes losses are also caused by tilt. It's a downward spiral. You lose a little bit because of bad luck, it affects you emotionally, you play worse, you lose more and you fall into downswing. ? Conversely, an upswing can make you believe that you are the best player in the world. When we are successful, even when we play badly, we will talk about upswing. You can't judge the quality of your game only by the swings you get.